International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP B/2 RESISTANT DOWNY BROME (CHEATGRASS)
(Bromus tectorum)


ALS inhibitors (B/2)

United States, Montana
INTRODUCTION DOWNY BROME (CHEATGRASS)
Downy Brome (Cheatgrass) (Bromus tectorum) is a monocot weed in the Poaceae family.  In United States this weed first evolved resistance to Group B/2 herbicides in 2016 and infests Wheat.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)).  Research has shown that these particular biotypes are resistant to imazamox, procarbazone-sodium, and pyroxsulam and they may be cross-resistant to other Group B/2 herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

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QUIK STATS (last updated Mar 21, 2017 )

Common NameDowny Brome (Cheatgrass)
SpeciesBromus tectorum
GroupALS inhibitors (B/2)
Herbicidesimazamox, procarbazone-sodium, and pyroxsulam
LocationUnited States
Year2016
Situation(s)Wheat
Contributors - (Alphabetically)Prashant Jha, and Vipan Kumar 
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Downy Brome (Cheatgrass) biotype with this Downy Brome (Cheatgrass) biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.
 
Genetics

Genetic studies on Group B/2 resistant Downy Brome (Cheatgrass) indicate that the inheritance is determined by a one gene trait.  There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature
 
Mechanism of Resistance

Studies on the mechanism of resistance of Group B/2 resistant Downy Brome (Cheatgrass) from United States indicate that resistance is due to an altered target site.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
 
Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes.  If you have any information pertaining to the fitness of Group B/2 resistant Downy Brome (Cheatgrass) from United States please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

PRASHANT JHA
Associate Professor-Weed Science
Montana State University-Bozeman
Southern Agricultural Research Center
748 Railroad Highway
Huntley, 59037, Montana
United States
Email Prashant Jha
Web   : Web Site Link
VIPAN KUMAR
Postdoctoral Research Associate
Montana State University
Southern Ag Research Center
748 Railroad Highway
Huntley, 59037, Montana
United States
Email Vipan Kumar
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in United States have been instrumental in providing you this information. Particular thanks is given to Prashant Jha, and Vipan Kumar for providing detailed information.
Herbicide Resistant Downy Brome (Cheatgrass) Globally
(Bromus tectorum)
Herbicide Resistant Downy Brome (Cheatgrass) Globally
(Bromus tectorum)
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Herbicide Resistant Downy Brome (Cheatgrass) Globally
(Bromus tectorum)
#CountryFirstYearSituationActive IngredientsSite of Action
1 FranceFrance 1981 Corn (maize) atrazine 17 Photosystem II inhibitors (C1/5)
40Bromus tectorumDowny Brome (Cheatgrass)457
2 SpainSpain 1990 Wheat chlorotoluron 38 PSII inhibitor (Ureas and amides) (C2/7)
40Bromus tectorumDowny Brome (Cheatgrass)190
3 SpainSpain 1990 Orchards simazine 38 Photosystem II inhibitors (C1/5)
40Bromus tectorumDowny Brome (Cheatgrass)191
4 United States (Oregon) United StatesOregon1997 Kentucky bluegrass imazamox, primisulfuron-methyl, and sulfosulfuron 45 ALS inhibitors (B/2)
40Bromus tectorumDowny Brome (Cheatgrass)1112
5 United States (Oregon) United StatesOregon2005 Grass seed clethodim, fluazifop-P-butyl, quizalofop-P-ethyl, and sethoxydim 45 ACCase inhibitors (A/1)
40Bromus tectorumDowny Brome (Cheatgrass)5375
6 United States (Montana) United StatesMontana2016 Wheat imazamox, procarbazone-sodium, and pyroxsulam 45 ALS inhibitors (B/2)
40Bromus tectorumDowny Brome (Cheatgrass)15071
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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Sunday, April 23, 2017 .  Available  www.weedscience.org
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